Different types of K+ channels in modeling of repetitive action potentials

Abstract

The data on the kinetics of voltage-dependent K § conductances studied in the somatic membrane of rat dorsal root ganglion (DRG) neurons were used in a model of repetitive generation of action potentials. Brief currents depolarizing the membrane from the potentials negative to -75 mV elicited more than one action potential, if a proper balance of outward and inward currents occurred in the final phase of repolarization. Low voltage-activated (LVA) Ca 2 § current was the most significant inward current in this balance, opposed by outward K § and leakage currents. Three types of voltage-activated K + currents found in DRG neurons played distinct roles in generation of repetitive action potentials. Inactivating D-type K* current directly influenced this generation, being a major outward current in the above-mentioned balance. Transient A-type K § current was largely inactivated in the final phase, but mediated generation of repeated spikes through inactivation of LVA Ca 2 § currents in the declining phase of an action potential. Non-inactivating delayed rectifier K* current was not involved in generation of repetitive spikes, because the membrane potential only briefly exceeded its activation threshold. The effect of Ca2 § -pendent K § currents was also negligible at short modeling lifespans, but its growth in the course of continuous oscillatory firing due to accumulation of Ca 2 § was possible.